GasExchg(2)

GasExchg(2) - General Biology 101 Dr. Morrison Lecture: Gas...

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General Biology 101 Dr. Morrison Lecture: Gas Exchange Question #1 Why is the largest insect smaller than a mouse? Question #2 Why do humans drown in water, but fish don’t? All gas exchange is by diffusion All organisms exchange gases (O 2 , CO 2 ) with their environments by diffusion . Diffusion is the net movement of molecules from areas of higher concentration to areas where they are in lower concentration. Diffusion of water molecules is “osmosis.” Requirements for gas exchange Four things are needed for gas exchange: A concentration gradient A moist membrane Adequate surface area Internal transport system Concentration gradient Diffusion occurs only down a concentration gradient, from areas of high concentration to areas of low concentration. For example, the diffusion of O 2 from your lungs into your blood. Moist membranes Diffusion occurs only across moist membranes. If aquatic, gas exchange surfaces can be external (e.g., gills). If terrestrial, gas exchange surfaces are usually internal (e.g., lungs). If small, diffusion alone is enough Diffusion through body fluids is very slow. Diffusion alone is good enough for gas exchange IF the distances O 2 has to diffuse are short (< 1 mm) If small (e.g., Paramecium , flatworms), diffusion alone is enough. In larger organisms
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This note was uploaded on 09/28/2010 for the course BIO 101 taught by Professor Martin during the Fall '08 term at Rutgers.

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GasExchg(2) - General Biology 101 Dr. Morrison Lecture: Gas...

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